The present invention relates to a new and improved construction of a front end-actuated push button or knob for electrical switches, hereinafter simply referred to as a push button.
Generally speaking, the push button of the present development, which is particularly used for the actuation of electrical switches, is of the type which is guided and retained in a cover plate or the like of a piece of equipment, such as a switchboard or control panel, and is manually actuated against the force of a pushing or ejection spring. In order to limit the actuation path of the push button there is provided a front, solid or rigid flange member, and for limiting the return or ejection path there is provided a rear impact or stop member.
Push buttons usually possess a rigid or solid front flange member. They are inserted into the cover plate from the front side or face thereof and thereafter secured against dropping-out by attaching a removable rear impact member. The push buttons are thus securely connected with the cover plate so that they cannot detach therefrom and become lost, and in this way there is ensured for a simple mounting or assembly of the cover plate upon the separately installed electrical switching apparatus or the like.
There have become known to the art push buttons containing different constructions of holder or retention devices for the removable rear impact members, such as for instance expandable rings formed of spring steel, mountable contact-making cable shoes and so forth.
In Swiss Pat. application No. 412,045 there has been disclosed a push button, wherein the rear impact or stop member consists of two parts which are joined together with the push button, namely a rubber O-ring and an impact or stop ring member possessing an angled or cornered cross-sectional configuration. The rear portion of the push button itself is equipped with a semi- circular-shaped circumferential groove. There is pushed onto the rear end of the push button inserted into the cover plate the impact ring member with the smaller internal diameter thereof leading. Thereafter, the rubber O-ring is placed into the circumferential groove and the impact ring member is pushed back downwardly over the rubber O-ring. Both of these auxiliary parts mutually secure one another; while the impact ring member is retained upon the push button by the action of the rubber O-ring, the impact ring member, in turn, prevents jumping-out of the rubber O-ring from the circumferential groove by means of its outer leg which encircles the rubber O-ring.
Apart from the advantages which such prior art construction of push button affords, such as assembly and disassembly without the need for auxiliary tools, or the impact member which is spring-loaded or resiliently biased by the rubber ring, nonetheless all of the heretofore known constructions of push buttons are afflicted with the common drawback that during the assembly thereof at a cover plate or the like they must be joined together from a number of separate parts, and they only can be mounted or removed if the cover plate is dismantled and there is afforded access from the rear side thereof.